The technique of in-mould labelling (IML) has been known for many years. It involves the use of paper or plastic labels which ultimately form an integral part of the moulded product. The in-mould labels must, therefore, be able to tolerate the heat applied during the moulding process. The resultant product is a pre-decorated item, such as a container or the like, which may be filled thereafter. In contrast to glue applied or pressure-sensitive labels which appear above the surface of the container, in-mould labels appear as part of the container. In-mould labels are greatly advantageous over traditional labels to be applied to an article after manufacturing thereof in that, the label is intimately bonded to the article and, therefore, highly resistant to ripping, scratching, peeling and other forms of label damage. Furthermore, in-mould labelling effectively eliminates the need for a separate labelling process following the manufacture of the container, which reduces labour and equipment costs.
In-mould labels can be used to cover a portion of a container or to cover the entire outer surface of a container. In the latter case, the in-mould label serves as an additional layer and may, therefore, enhance the structural integrity of the container, or add to the barrier performance of the container. Even in the former case, the labelled container may be strengthened in the region of the applied label as a result of the structural contribution made by the label.
In-mould labels generally comprise a carrier base, consisting of a polymeric or biopolymeric carrier film, on which a decorative pattern or a written message is printed. The adhesion of such labels to a polymeric article can be enhanced by applying a heat sealable layer (e.g. a film or a coating) onto the backing side (i.e., not printed surface) of the in-mould label which is to be in contact with the polymeric article. The in-mould label may be cut to the desired shape and size from a larger sheet of the label material, using label cutting apparatus.
In conventional in-mould labelling processes, a cut-out label is positioned against a wall of a mould for injection moulding or for blow moulding or the like and held in place by means such as electrostatic force, vacuum suction or a handling unit, and a polymeric article is moulded by injecting a mass of polymeric melt or by blowing a polymeric parison against the mould walls on which the in-mould label is held.
Problems associated with conventional in-mould labelling processes include high operating costs, low output and the requirement of complex mechanical equipment for steps such as positioning the label within the mould.
JP 2010-143136 discloses an apparatus for obtaining an in-mould labelled article using injection moulding. The apparatus comprises a label cutter which punches out a label from a label tape and then advances and holds the label at the surface of a cavity of a mould, the cavity is filled with resin and the in-mould labelled article is formed.
JP 63-252718 discloses a method for decorating a hollow moulded object with a pattern, wherein a transferring foil with a printing layer is inserted into a mould, and said printing layer is transferred onto a hollow moulded object in the process of moulding the hollow moulded object.
JP 4-175141 discloses a process for making a blow moulded product which includes the steps of positioning a sheet having a surface pattern which is incompatible with a parison in a mould for blow molding; extruding a softened parison of a synthetic resin from a die head; holding the parison in the mould and blowing gas into the parison to be expanded to form a blow moulded product with a surface feature of the sheet reproduced on the blow moulded product; and separating the sheet and the blow moulded product from each other.
GB 1,031,518 discloses a method of blow moulding an article from a hot tubular blank extruded into a mould, a printed sheet is inserted between the mould wall and the blank and is bonded with the wall of the hollowed article formed. A similar process is disclosed in U.S. Pat. No. 3,227,787.
EP 0 324 857 discloses a moulding machine consisting of an injection moulding unit for moulding a preform; a rotary moulding machine which is adapted to receive the preform directly or after the temperature thereof has been regulated, and which has a draw-blow moulding unit provided with a blow mould for moulding the preform into a hollow container and a moulded product recovering unit; and a label insert unit. The unit is composed of a label supply means positioned on one side of the blow mould, a driving means for moving the label supply means towards and away from the blow mould, and a label magazine disposed at the front side of the label supply means.
EP 0 822 048 discloses a foil-decorating injection moulding method which adjusts the tension of a decorative sheet so that the decorative sheet may not break, slip off a clamper, crease or be dislocated when the clamper clamps the decorative sheet.
DE 1805328 discloses a method of forming decorations on compression-moulded articles which comprises introducing a decoration into a mould and forming an object by contacting it with the decorative pattern, wherein the decoration is introduced into the mould wall by a reciprocating piston.
U.S. Pat. No. 4,501,548 discloses a label transferring device for blow moulding machines which includes a sliding mould insert with a plurality of label carrying segments which are shifted into an access aperture communicative with the mould cavity. A label transfer arm assembly removes a label from a supply magazine and places the label on one exposed label carrying segment while another label carrying segment is within the mould cavity undergoing the moulding and label attachment process.
U.S. Pat. No. 4,824,630 discloses a method for applying labels in the moulds of a plastic blow-moulding machine of the type wherein a plurality of sets of moulds are mounted on a wheel rotatable about a horizontal axis and the moulds are moved toward and away from one another to enclose a parison and the parison is then blown to the confines of the cavity between the mould sections, which comprises successively die punching labels from a web directly onto vacuum cups and delivering the labels successively between the mould sections.
Other in-mould labelling techniques are disclosed in, CN 201334143, JP 3-26524, JP 2-41224, US 2003/0099793, US 2004/0056389 and WO 93/04842.
In-mould labelled articles are used in a wide range of industries and due to an increasing social demand, it is becoming more common for the articles in question to be recycled, particularly those articles made of non-biodegradable materials. When such articles are returned by the consumer, they may be cleaned to remove any traces of their previous contents and commonly, the in-mould labels are removed from the articles so that either or both can be recycled.
Problems associated with methods known in the art for removing in-mould labels from articles include high operating costs which can render the recycling process uneconomically viable and the requirement of complex mechanical equipment.
WO 2006/054725 discloses an in-mould labelled article in which an in-mould label having a thermoplastic resin-containing substrate layer and a heat-seal layer that contains a heat-seal resin and a water-soluble binder is stuck to a shaped article and in which the in-mould label does not peel off from the shaped article even when the labelled in-mould shaped article is dipped in water at 40° C. for 4 days.
U.S. Pat. No. 7,807,243 discloses a label for in-mould forming having excellent suitability for de-labelling. The in-mould labelled container is de-labelled by applying a temperature of 90° C. in a thermostatic chamber.
EP 1 553 126 discloses a stretch resin film having a liquid absorption coefficient of at least 5 ml/(m2·ms1/2). The document also discloses a de-labellable label which is removed from an object when sprayed with water at a pressure of 2 MPa.
U.S. Pat. No. 6,165,576 discloses in-mould plastic labels which are provided with separation interfaces whereby the printed surfaces of the labels and the contaminating printing inks associated with them can be removed so as to allow recycling of the bottle stock without contamination by the printing inks.
U.S. Pat. No. 5,110,055 discloses apparatus and a method for its use in cleaning comminuted thermoplastic material for reuse in manufacture of moulded plastic products. Batches of plastic including adherent label materials and adhesives are agitated by a rotor until frictionally heated to a predetermined temperature. A flow of air is used to carry away loosened labels and adhesives. A small amount of water is introduced as a spray to dissolve adhesives and soften remaining label materials further, while loosened pieces continue to be removed in a stream of air. Thereafter, remaining adherent particles are removed in an aspirator providing a multi-stage cascade through counter-currents of air, and the particle-carrying air is then cleaned in a cyclone separator.
Other in-mould label removal techniques are disclosed in WO 2005/120963 and JP 7-92913.